Mesenchymal stem cells (MSC), expanded from bone marrow aspirates, have demonstrated immunosuppressive and regenerafive properties in animal models. While human clinical trials have been initiated in graft versus host disease, autoimmune disorders, and musculoskeletal regenerafion, applicationto transplants has lagged behind. Murine and pre-clinical experimental models have raised specific concerns of allo-sensitization, reproducibility of MSC phenotypic and functional characterization, and optimal indication post-transplant In this Project 2 of the Program, efficacy studies will be undertaken to define optimize immunosuppressive and regenerative funcfions of MSC. In aim 1, we will test whether interferon gamma activated MSC provide greater homogeneity in form and function when compared to non-activated MSC and we will define the relafive contribufion of MHC matched MSC to mismatched ones on renal allograft function in the setting of a sub-therapeufic immunosuppressive regimen. We will test the efficacy of MSC in reducing tissue injury from prolonged cold ischemia fimes in Aim 2 and in Aim 3, through the collaborafion with Cores B and C, the secondary outcome measures which include longitudinal assessments of immune responses, tissue biopsies, and endothelial progenitor frequencies will be correlated to the primary outcome measure, 100-day rejecfion free survival, to define efficacy. Assessments will be undertaken proteomically and genomically via Core B and then compiled and stafisfically analyzed in Core C using both classical statisfics and a novel machine learning approach which has the potential to maximize data analysis from small sample sizes. These efficacy studies will be undertaken in a pre-clinical renal transplant model to parallel similar studies in a pre-clinical islet model in Project 1. Synergy between this project, Project 1, and Cores B and C will be facilitated by the Administrative Core, which will coordinate monthly conference calls, track samples to the Cores, and follow the progress on timelines and deliverables. These studies support our long-term goal, which is to demonstrate MSC efficacy or non-efficacy in minimizing baseline immunosuppression.